Ground State of Underdoped Cuprates in Vicinity of Superconductor-to-Insulator Transition

Abstract

When an insulating underdoped cuprate is doped beyond a critical concentration (xc), high-temperature superconductivity emerges. We have synthesized a series of La 2−xSr xCuO 4 (LSCO) samples using the combinatorial spread technique that allows us to traverse the superconductor-to-insulator transition (SIT) in extremely fine doping steps, Δx≈0.00008. We have measured the Hall resistivity (ρH) as a function of temperature down to 300 mK in magnetic fields up to 9 T. At very low temperatures, ρH shows an erratic behavior, jumps and fluctuations exceeding 100 %, hysteresis, and memory effects, indicating that the insulating ground state is a charge-cluster glass (CCG). Based on the phase diagram depicted in our experiment, we propose a unified picture to account for the anomalous electric transport in the vicinity of the SIT, suggesting that the CCG is in fact a disordered and glassy version of the charge density wave.

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Acknowledgments

The experimental work was done at the Brookhaven National Laboratory and was supported by the US Department of Energy, Basic Energy Sciences, Materials Sciences and Engineering Division. I.B. was supported in part by the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant GBMF4410.